Position sensitive mechanical feedback control

ABSTRACT

A power mechanism having a control member and a power delivery member connected to respective ends of a wrap spring wound around a continuously rotating shaft. The control member is adapted to follow a universal bar and, in response to movement of the universal bar in a predetermined direction, to cause the wrap spring to couple the power delivery member to the continuously rotting shaft until the power delivery member is driven through an angle equal to that traveled by the control member.

United States Patent ml 1 [72] Inventor Arthur R. Johnson 2,875,8803/1959 Palmer 197/17 Wethersfield, Conn. 2,973,078 2/1961 Templeton eta1, 197/17 [21] Appl. No 762,695 3,077,971 2/1963 Palmer 197/71X [22]Filed Sept. 26,1968 3,086,635 4/1963 Palmer 197/16 [45] Patented June1,1971 3,157,265 11/1964 Palmer 197/16 [73] Assignee Litton BusinessSystems, Inc. 3,191,740 6/1965 Smusz et a1. 197/16 New York, N.Y.3,348,648 10/1967 Frechette 197/16 3,349,886 10/1967 Madison et a1.197/107 [54] POSITION SENSITIVE MECHANICAL FEEDBACK CONTROL 2 Claims, 2Drawing Figs.

[52] U.S.Cl 197/17, 197/97 [51] Int. Cl B41j 23/08 [50] Field of Search197/16, 17,

[56] References Cited UNITED STATES PATENTS 1,936,466 11/1933 Crumrine197/97 2,155,997 4/1939 Sterling 197/97X Primary Examiner-Ernest T.Wright, Jr. Attorney.loseph R. Spalla and Cornelius P. Quinn ABSTRACT: Apower mechanism having a control member and a power delivery memberconnected to respective ends of a wrap spring wound around acontinuously rotating shaft. The control member is adapted to follow auniversal bar and, in response to movement of the universal bari-inapredetermined direction, to cause the wrap spring to couplethe powerdelivery member to the continuously rotting shaft until the powerdelivery member is driven through an angleequal to that traveled by thecontrol member.

PATENTED JUN Il97l 3 5 1,859

INVENTOR ARTHUR R. JOHNSON BY 5% M ATTORNEY POSITION SENSITIVEMECHANICAL FEEDBACK CONTROL BACKGROUND OF TH E INV ENTION This inventionrelates to mechanisms for transmitting power to auxiliary mechanisms inan electric typewriter at a rate related to the movement of individualtype actions, and more particularly it relates to a power transmittingmechanism which delivers power at a velocity directly related to andsubstantially over the interval of movement of a universal bar driven byindividual type actions.

It is well known in electric typewriters having type actions of the typebar type for each of the type actions to include a sublever operative todrive a universal bar. The universal bar when driven by any one of thesublevers often operates auxiliary mechanisms, for lifting ribbon,tripping an escapement and in some instances even feeding a ribbonthrough the machine.

In order to produce high quality print work in a type bar machine it isnecessary to maintain the velocity of a driven type bar and its impactwith the platen within relatively close tolerances, otherwise the colordensity of the print work will not be constant and a mixture of lightand dark type impressions will result.

Unfortunately, the power demands made by these auxiliary mechanisms arenot constant and often impose variable loads on the type actions whichvary the velocity of a driven type bar and its impact with the platenbeyond allowable limits, consequently impairing the quality of the printwork.

While it has been suggested in the prior art to use a power mechanismtriggered by the universal bar to drive the auxiliary mechanisms so asto remove the load of the auxiliary mechanismsfrom the type actions,these prior art devices have not been entirely satisfactory. In theknown prior art devices, the power mechanisms are cyclic and once thepower mechanism is triggered by the universal bar, the power mechanismoperates through a preset cycle independently of the universal bar.Thus, the time interval in which any particular auxiliary mechanism goesthrough its cycle of operation is constant regardless of whether theuniversal bar is actuated by an action associated with a center type baror an action associated with an end type bar. Consequently, the powermechanism cannot be retriggered until it has completed a preset cycleresulting in delays, which in some instances such as calling for anewcharacter, is particularly objectionable. Also, in the case of anauxiliary mechanism such as a ribbon lift, for example, since the timeinterval between a type bar leaving its headrest and striking a platenincreases progressively from the center type bar to an end type bar, inorder to insure that the ribbon is in front of the type bar when thetype bar strikes the platen, means must be provided to adjust thetriggering time of the power mechanism for each individual type action,either by providing an irregular shaped universal bar or by varying thecam surface of each sublever.

SUMMARY OF THE INVENTION The present invention provides an electrictypewriter having a plurality of type actions and a universal bar drivenby the type actions, with a power mechanism for powering auxiliarymechanisms such as a ribbon lift mechanism as well as escapement tripmechanisms and the like, in response to the movement of the universalbar and at the rate of or a rate related to the movement of theuniversal bar. The power mechanism has a control member and a powerdelivery member connected to respective ends of a wrap spring woundabout a continuously rotating shaft. The control member is responsive tomovement of the universal bar and is followed by the power deliverymember which is caused to be coupled to the continuously rotating shaftby the wrap spring during movement of the control member in apredetermined direction and at the rate of movement of the controlmember.

Accordingly, one of the objects of the present invention is to providean electric typewriter for producing print work of constant colordensity.

Another object of the present invention is to eliminate any variationsin type bar velocity and impact with the platen as a result of the powerdemands of auxiliary mechanisms.

Another object of the present invention is to divorce the type actionsfrom the effect of the power demands necessary to operate auxiliarymechanisms.

Another object of the present invention is to provide a power mechanismin which the velocity of power delivered to the auxiliary mechanisms hasa direct relation to a control velocity.

Still another object of the present invention is to provide a noncyclicpower mechanism for delivering power to the auxiliary mechanisms at avelocity having a direct relation to the velocity ofa universal bar.

Other objects and advantages of the present invention will becomeobvious to those skilled in the art from a consideration of thefollowing description read in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of aportion of an electric typewriter embodying the power mechanism of thepresent invention.

FIG. 2 is a front elevation view partly in section of the powermechanism of the present invention in a normal inoperative position.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring nowto the drawing wherein like reference characters designate like orcorresponding parts throughout the several views, the power assistmechanism of the present invention is shown in conjunction with anelectric typewriter employing type bars. As illustrated in FIG. 1, aportion of a sublever 10 is pivotally mounted on a shaft 12 secured tothe frame and is articulately connected by a link 14 to a type bar 16pivotally mounted on a segment wire 18. The sublever 10 is adapted to bepivoted counterclockwise as viewed in FIG. I by powered actuating means(not shown) to drive the type bar 16 from a headrest 113 into contactwith a platen 20. A return spring 22 connected to the sublever 10returns the type bar 16 and sublever 10 to their normal positions aftertyping impact with the platen 20.

A forwardly extending tail 24 of the sublever 10 overlies a universalbar 26 pivotally mounted on the shaft 12 so that when the sublever 10 ispivoted counterclockwise the universal bar 26 is also pivotedcounterclockwise, and when the sublever 10 returns to its normalposition, the universal bar 26 is returned to a normal clockwiseposition against a stationary stop 27 by a spring 28 connecting theuniversal bar 26 to the machine frame.

A power assist mechanism generally designated by the numeral 32comprises two levers, a control lever 34 and a power delivery lever 36,rotatably mounted between a pair of bushings 37 and 39 on a continuouslycounterclockwise rotating shaft 38 extending from the end of a powerroll or snatch roll (not shown). The control lever 34 is articulatelyconnected to the universal bar 26 by a link 30 and the power deliverylever 36 is connected to an auxiliary mechanism (not shown) by a link49.

The control lever 34 and the power delivery lever 36 are connectedtogether by a wrap spring 40 wrapped clockwise from right to left aboutthe rotating shaft 38 as viewed in FIG. 2. A control end 45 of the wrapspring 40 is received in a slot 41 in the control lever 34 and adelivery end 46 of the wrap spring 40 is received in a slot 48 in thepower delivery lever 36. The wrap spring 40 is wound that clockwiserotation of the control lever 34 urges the wrap spring 40 to open asdoes counterclockwise rotation of the power delivery lever 36.

Counterclockwise rotation of the control lever 34 causes the wrap spring40 to grip and to be driven by the continuously rotating shaft 38thereby to transmit driving movement to the power delivery lever 36until the power delivery lever 36 reassumes its normal angular positionrelative to the control lever 34 following cessation of control levermovement in counterclockwise direction.

The wrap spring 40 is wound in an interference fit with the shaft 38 asshown in H6. 2 when an immediate sensing response is desired, or with aslight clearance if an initial motion response delay is acceptable. Thecontrol lever 34 is biased in a normal clockwise position by the spring28 urging the universal bar 26 clockwise against the stationary stop 27,and the power delivery lever 36 is biased in a normal clockwise positionby a spring 42 connected to the power delivery lever 36 urging the powerdelivery lever 36 clockwise against a stationary stop 44.

In operation, as the sublever l pivots counterclockwise to drive thetype bar 16 into contact with the platen 20, the forwardly extendingtail 24 of the sublever pivots the universal bar 26 counterclockwise.

counterclockwise movement of the universal bar 26 moves the controllever 34 counterclockwise allowing the wrap spring 40 to grip thecounterclockwise rotating shaft 38 which power drives the wrap spring 40until the power delivery lever 36 reassumcs a normal angular positionrelative to the control lever 34 following cessation ofcounterclockwisemovement of the universal bar 26 and control lever 34. After the typebar 16 has impacted against the platen 20 and begins its return to headrest 13 the universal bar 26 also begins to return in a clockwisedirection, under the action of the spring 28, into abutment with thestop 27. During this clockwise return movement the control lever 34moves clockwise urging the wrap spring 40 to open and allowing the powerdelivery lever 36 to move clockwise under the action of the spring 42until the control and power delivery levers 34 and 36 reassume theirnormal angular clockwise relationship. Any tendency of the wrap spring40 to wrap from left to right during the return movement of lever 36 byspring 40 will be opposed by the counterclockwise rotating shaft 38.Should another type action be initiated during return movement of theuniversal bar 26, the sublever 10 of the next called action will arrestand reverse the direction of the universal bar 26 and again causeimmediately the actuation of the power assist mechanism 32.

With the power assist mechanism 32, the link 49 connected to the powerdelivery lever 36 is used to transmit the power from the continuouslyrotating shaft 38 to operate the auxiliary mechanisms of the typediscussed previously.

As a result, instead of requiring the universal bar 26 to transmit powerfrom the sublever 10 which will result in a variable load being imposedon the type action, or requiring it to actuate a power mechanism, withthe velocity output of the power mechanism independent of the velocityof the universal bar 26, the universal bar 26 in accordance with theinvention now merely moves with the sublever 10, without loadingsublever [0, and the motion of the universal bar 26 is sensed andfollowed by the control lever 34 of the power assist mechanism 32 whichthen supplies all of the power necessary to drive the auxiliarymechanisms from the rotating shaft 38, at the rate of movement of theuniversal bar 26. Thus the load is divorced from the universal bar 26and type action. As a consequence there is eliminated the need for anirregular shaped universal bar 26 or other such means for varying thetriggering time of the power mechanism for each type action. Also, sincethe power assist mechanism 32 is noncyclic it is always prepared todeliver power to an auxiliary mechanism lever 34, and the link 49 on thepower delivery lever 36.

The invention I claim is:

1. In an electric typewriter, a power assist mechanism for poweroperating a function control element in response to and at the rate ofmovement of a type action driven universal bar from a rest position,comprising,

means biasing said universal bar toward said rest position,

a driven shaft,

a control lever and an output lever rotatably mounted on said drivenshaft,

a coiled spring coaxially wound around said driven shaft in a directionopposite the direction of rotation of said driven shaft and connected atone end to said control lever and at its other end to said output lever,

means biasing said output lever to a rest position, said coiled spring,with said universal bar and said output lever at rest position, beingeffectively disengaged from said driven shaft, and

means connectingsaid universal bar to said control lever whereby duringmovement of said universal bar from said rest position said coiledspring is caused to be coupled to, and to be driven by, said drivenshaft at a rate of movement proportional to that of said universal barmovement and in turn to drive said output lever.

2. In an electric typewriter having, a type action, a universal barmovable in a first direction in response to power driven movement ofsaid type action, and a function control link for operating an auxiliarymechanism in response to movement of said universal bar, the improvementcomprising,

power assist means connected between said universal bar and saidfunction control link for sensing, without resisting, movement of saiduniversal bar in said first direction and, in response, power operatingsaid control link during continued movement of said universal bar insaid first direction, and at a rate of change of movement proportionalto the movement of said universal bar in said first direction, saidpower assist means including a continuously rotatable shaft,

a control lever rotatably mounted on said continuously rotatable shaftarticulately connected to said universal bar,

a power delivery lever rotatably mounted on said rotatable shaft andarticulately connected to said function control link,

a wrap spring telescoping said continuously rotatable shaft, said wrapspring having a control end and power delivery end, said control endbeing connected to said control lever thereby to follow the movement ofsaid universal bar in said first direction and during said movement tocause said wrap spring to frictionally engage said continuouslyrotatable shaft and be driven until said power delivery end has movedthrough substantially the same angular distance as said control endfollowing cessation of universal bar movement in said first direction,said power delivery end of said wrap spring being connected to saidpower delivery lever,

and means biasing said power delivery lever and said universal bar in asecond direction to a rest position.

1. In an electric typewriter, a power assist mechanism for poweroperating a function control element in response to and at the rate ofmovement of a type action driven universal bar from a rest position,comprising, means biasing said universal bar toward said rest position,a driven shaft, a control lever and an output lever rotatably mounted onsaid driven shaft, a coiled spring coaxially wound around said drivenshaft in a direction opposite the direction of rotation of said drivenshaft and connected at one end to said control lever and at its otherend to said output lever, means biasing said output lever to a restposition, said coiled spring, with said universal bar and said outputlever at rest position, being effectively disengaged from said drivenshaft, and means connecting said universal bar to said control leverwhereby during movement of said universal bar from said rest positionsaid coiled spring is caused to be coupled to, and to be driven by, saiddriven shaft at a rate of movement proportional to that of saiduniversal bar movement and in turn to drive said output lever.
 2. In anelectric typewriter having, a type action, a universal bar movable in afirst direction in response to power driven movement of said typeaction, and a function control link for operating an auxiliary mechanismin response to movement of said universal bar, the improvementcomprising, power assist means connected between said universal bar andsaid function control link for sensing, without resisting, movement ofsaid universal bar in said first direction and, in response, poweroperating said control link during continued movement of said universalbar in said first direction, and at a rate of change of movementproportional to the movement of said universal bar in said firstdirection, said power assist means including a continuously rotatableshaft, a control lever rotatably mounted on said continuously rotatableshaft articulately connected to said universal bar, a power deliverylever rotatably mounted on said rotatable shaft and articulatelyconnected to said function control link, a wrap spring telescoping saidcontinuously rotatable shaft, said wrap spring having a control end andpower delivery end, said control end being connected to said controllever thereby to follow the movement of said universal bar in said firstdirection and during said movement to cause said wrap spring tofrictionally engage said continuously rotatable shaft and be drivenuntil said power delivery end has moved through substantially the sameangular distance as said control end following cessation of universalbar movement in said first direction, said power delivery end of saidwrap spring being connected to Said power delivery lever, and meansbiasing said power delivery lever and said universal bar in a seconddirection to a rest position.